Electromechanical driver for an aerosol dispensing apparatus which dispenses a medicated vapor into the lungs of a patient

ABSTRACT

An aerosol dispensing apparatus comprises a housing which includes a top  l having a sharp edged orifice and a speaker assembly mounted on a bottom portion of the housing. A sawtooth waveform generator generates and then provides a sawtooth waveform signal which includes a jitter component to the speaker assembly which drives a flexible diaphragm resulting in a reciprocating motion of the flexible diaphragm. The ramp portion of sawtooth waveform signal retracts the flexible diaphragm in a rearward direction, while the approximately vertical portion of the signal causes an abrupt forward movement of the flexible diaphragm. The inner portion of the housing forms a chamber which contains a medication. The jitter component of the sawtooth waveform signal fluidizes the medication suspending the medication in air within the chamber to form a vaporized medication. Each cycle of the sawtooth waveform signal generates one ring vortex of a train of ring vortices with the ring vortex being generated during the vertical portion of the signal when the abrupt forward movement of the flexible diaphragm occurs.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to medical treatment apparatus.More specifically, the present invention relates to an electromechanicaldriver which may be used with a ring vortex aerosol projection apparatusfor providing medication in a vapor form to the lungs of a patienthaving asthma or a like medical condition.

2. Description of the Prior Art

Patients suffering from asthma or any of the many other lung diseasesrequire delivery of medication to the bronchial tubes and the alveolarair sachs in the lungs. At the present time there are three major waysof delivering aerosol treatment or medication to such patients, namely(1) nebulizers, which may be of the (a) venturi-jet type, or of the (b)ultrasonic piezoelectric type which produce aerosols from drugsolutions; (2) metered dose inhalers (MDI) consisting of fluorocarbon orother gas pressurized canisters; and (3) dry powder inhalers (DPI) whichmay be (a) passive or (b) active. Dry powder inhalers also providemetered doses if sufficient suction is supplied by the patient.

Present day nebulizers for delivering medication to the lower recessesof the lungs are inefficient in that they deliver only 20 percent of themedicated aerosol beyond the trachea. The remainder of the vapor passesthrough the throat into the patient's stomach. This may result inserious side effects when a potent medication such as Pentamidine isbeing use to treat a patient lung disease. Increasing the dosage tocompensate for the delivery inefficiency of the nebulizer may also beharmful to the patient.

While nebulizers can achieve the desired particle size of from 0.5microns to 5.0 microns for the medication being delivered to the lungs,they are very inefficient in delivery of the medication to the lungs,especially the smallest bronchial tubes and alveolar air sachs of thelungs.

In addition, since a relatively small percentage of the medicationreaches remote areas of the lung, the treatment may be ineffective,especially in smoke inhalation cases, pneumonia, or severe asthmaattacks. In the case of smoke inhalation or severe asthma attacks, themedication which comprises generally anti-inflammatory drugs needs toreach the affected area of the lungs as quickly as possible to preventpermanent damage to the lungs and possible loss of life.

Metered dose inhalers which are both MDI and DPI have certain advantagesover nebulizers because they are readily portable, and do not generallyrequire an external power source such as compressed air or electricity.Metered dose inhalers are also capable of generating aerosols that aresuitable for inhalation, more efficiently, reliably and costeffectively. The pressurized canister type of aerosol generator (MDI)includes a valve, which, when actuated, causes dispersement of a meteredquantity of drug.

Because metered dose inhalers have previously used a chlorofluorocarbonas the propellant, and chlorofluorocarbons are believed to have a highlyadverse effect on the ozone layer surrounding the earth, they aregradually being phased out to be replaced by the environmentally morefriendly hydrofluorocarbons (e.g., HFC 134a and 227).

Such metered dose inhalers have become popular in that a droplet aerosolconsisting of the drug particles and the fluorocarbon propellant isgenerated. The fluorocarbon propellant evaporates rapidly, and leavessmaller drug particles and clumps of particles, at least some of whichare on the order of 1-3 microns aerodynamic mass median diameter whichis the ideal size range for medication aerosols in humans.Unfortunately, many of the particles remain in larger clumps, and do notreach the necessary areas in the bronchi and lungs.

For example, some metered dose inhalers are relatively inefficientbecause they produce mainly non-respirable particles that range in sizefrom about 35 micro-meters to about 1 micrometers. Of these particlesonly about 30 percent, chiefly particles under 5 micrometers, areactually capable of being inhaled. In practice this figure is closer to20 percent. Most of the rest of the aerosol which is deposited in thethroat has the potential for causing side effects, while notcontributing to the therapeutic benefit.

There are some currently available powder inhalation systems which donot require a propellant. However, they do not function very effectivelyunless the patient can generate significant air flow rates, since it isthe energy provided by the patient's forceful inhalation that not onlymobilizes the powder but also breaks up the clumps thus preparing it forinhalation, in contrast with the high pressure of the fluorocarbon orother propellant in metered dose inhalers which accomplish the same end.

The patient's inhalation then carries the medication aerosol into theair passages via a mouthpiece. Current powder inhaler systems requirestrong inhalation on the part of the patient. They have not workedeffectively with patients who cannot inhale vigorously.

In the metered dose inhalers noted above, it is common practice toinclude surfactants such as oleic acid. This presents problems. Thefluorocarbon-medication suspension emerges as a liquid jet from the endof the valve stem or from the end of a cannula attached to the valvestem through which the metered dose inhaler contents have been forcedand about 80 percent of it is deposited within three or four centimetersof the end of the valve or cannula. This results in an inefficientdelivery system. It further has the disadvantage that large amounts ofthe surfactant material is deposited on the lining of the trachea, andthe first few bronchi. It has been demonstrated that this causes injuryto the airway lining with ulceration.

Over about the last 25 years systems for delivering medications to thelungs such as aerosol type delivery systems have become increasinglyimportant for the treatment of airway diseases, particularly asthma andchronic obstructive pulmonary diseases, such as chronic bronchitis andemphysema as well as bronchiolitis and bronchiectasis. Other aerosolmedications include mucolytic agents to thin secretions, the newest ofwhich is deoxyribonuclease made by a recombinant method (rhDN-ase).

It is becoming increasingly important to deliver antibiotics directly tothe airway for chronic illnesses such as cystic fibrosis, for treating atype of pneumonia in immunosuppressed patients (e.g., in AIDS), and forproviding a new class of medications (sodium channel blockers) in cysticfibrosis to "lubricate" the secretions and make them easier to cough upor remove as a result of the action of cilia.

Aerosol systems for delivering medication directly to the patient'slungs generally fall into one of two categories, either (1) active or(2) passive. "Active" devices include (a) metered dose inhaler and (b)wet nebulizers. The pressurized canister metered dose inhaler generatesthe aerosol and directs it towards the patient independently of thepatient's force of inhalation. This provides aerosol to the patient in amanner similar to so called "wet nebulizers" that aerosolize a drugsolution. These "wet nebulizers" are jet nebulizers using the venturiprinciple, the energy source being compressed air which also serves todirect aerosol towards the spontaneously breathing or ventilationassisted patient, and ultrasonic nebulizers utilizing high speedvibration of a piezo-electric crystal and a blower fan to carry themedication aerosol to the patient. These are all active aerosol devices,since with the jet nebulizer it is the flow of oxygen or air through thedevice that creates the aerosol and drives it towards the patient whocan then breathe in from a mouthpiece or mask. The ultrasonic nebulizergenerates the aerosol into a space from which it can be inhaled by thepatient breathing normally to inhale the mist with each inhalation, evenif that inhalation is not vigorous. In addition, a blower can beincorporated which pushes the aerosol from the ultrasonic generatortoward a mask or mouthpiece from which the patient inhales.

In contrast, currently available powder inhalers are "passive" devicesin that the drug powder must reside in a small reservoir from which thepatient can suck it by creating a relatively high inspiratory flow rate,usually over 30 liters per minute, and sometimes as high as 90-120liters per minute if the optimum dose of medication is to be provided.This type of device has the advantage that aerosol is inhaledautomatically when the patient inhales vigorously, but has certaindisadvantages in that (a) there is considerable variability in dosedepending upon how vigorously the patient inhales; (b) during severeepisodes of asthma it may not be possible to create the high flow ratesnecessary to get a full dose of the drug which is particularly true ofchildren under the age of 6; and (c) the greatest efficiency for aerosolinhalation is achieved at low inspiratory flow rates, 45 liters perminute and below, because at high flow rates small particles havegreater inertia and therefore act like larger particles, thereby tendingto be deposited in the back of the throat and around the larynx byimpaction rather than being carried into the airways of the lungs wherethe medication must be deposited to be effective.

Another disadvantage of some widely prescribed current powder systemsrelates to exposure to the humidity of the environment of the drugreservoir where the fine particles are stored. Since many drug particlesare very hygroscopic, repeated or continual exposure to humidity willgreatly reduce the available dose due to swelling and clumping.

In view of the foregoing, what is needed is a relatively simple, yethighly effective aerosol dispensing apparatus which will effectivelyprovide medication in a mist or vapor form to the bronchial tubes andthe alveolar air sachs of the lungs of a patient without requiring thepatient to inhale vigorously.

SUMMARY OF THE INVENTION

The present invention overcomes some of the disadvantages of the priorart including those mentioned above in that it comprises a relativelysimple yet highly reliable and efficient dispensing apparatus whicheffectively provides medication in a mist or vapor form to the bronchialtubes and the alveolar air sachs of the lungs of a patient withoutrequiring the patient to inhale vigorously.

In its simplest embodiment the dispensing apparatus comprises a housingwhich includes a top wall having a sharp edged orifice and a speakerassembly mounted on a bottom portion of the housing. The speakerassembly when energized drives a cone shaped flexible diaphragm of thespeaker assembly with a reciprocating motion. Connected to the speakerassembly is a sawtooth waveform generator. The sawtooth waveformgenerator generates and then provides a sawtooth waveform signal whichincludes a jitter component to the speaker assembly driving the flexiblediaphragm which results in the reciprocating motion of the flexiblediaphragm. The ramp portion of sawtooth waveform signal retracts theflexible diaphragm in a rearward direction, while the approximatelyvertical portion of the signal causes an abrupt forward movement of theflexible diaphragm.

The inner portion of the housing forms a chamber which contains amedication which may be either in liquid form or powdered form. Thejitter component of the sawtooth waveform signal fluidizes themedication within the chamber above the upper surface of the flexiblediaphragm. Fluidizing the medication suspends the medication in airwithin the chamber to form a vaporized medication.

Each cycle of the sawtooth waveform signal generates one ring vortex ofa train of ring vortices with the ring vortex being generated during thevertical portion of the signal when the abrupt forward movement of theflexible diaphragm occurs. During the ramp portion of the signal airfrom the atmosphere is drawn into chamber of the aerosol dispensingapparatus.

In another embodiment of the present invention, the aerosol dispensingapparatus may include multiple sharp edged orifices with each orificehaving a counterflow ring positioned around the orifice.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a simplified schematic diagram of an aerosol dispensingapparatus for dispensing a medicated mist which constitutes oneembodiment of the present invention;

FIG. 2 is a simplified schematic diagram of another embodiment of theaerosol dispensing apparatus of the present invention;

FIG. 3 illustrates the waveform used to drive solenoid of the aerosoldispensing apparatus of FIGS. 1 and 2;

FIG. 4 is a schematic diagram of a multiple counter-flow orifice aerosoldispensing apparatus which constitutes a third embodiment of the presentinvention;

FIG. 5 is an enlarged view of one counter flow orifice of the aerosoldispensing apparatus of FIG. 4; and

FIG. 6 is a schematic diagram of a single counter-flow orificedispensing apparatus which constitutes a fourth embodiment of thepresent invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to FIGS. 1 and 3, there is shown an aerosol dispensingapparatus, designated generally by the reference numeral 20, fordispensing a medicated vapor or aerosol medication into the lungs of apatient having asthma or a like medical condition. Aerosol dispensingapparatus 20 generates a train of ring vortices 22 which exit dispensingapparatus 20 through a sharp edged orifice or opening 24 located at thetop wall 25 of apparatus 20 in the manner indicated by arrow 26 prior toentering the lungs of a patient. The medicated vapor then enters thebronchial tubes and the alveolar air sachs of the patient's lungstreating the patient's medical condition.

Aerosol dispensing apparatus 20 comprises housing 28 which includes atop wall 25 and a speaker assembly 30 mounted on a bottom portion ofhousing 28. Speaker assembly 30 when energized drives a cone shapedflexible diaphragm 32 of the speaker assembly 30 with a reciprocatingmotion. Speaker assembly 30 also has a coil 34 which is coupled toflexible diaphragm 32 and a permanent magnet 35. Connected to thewinding 34 of speaker assembly 30 is a sawtooth waveform generator 36.Generator 36, in turn, generates and then provides the sawtooth waveformsignal 38 which includes a jitter component 40 to the winding 34 ofspeaker assembly 30 driving cone shaped flexible diaphragm 32 whichresults in the reciprocating motion of flexible diaphragm 32. The rampportion of sawtooth waveform signal 38 retracts flexible diaphragm 32 ina rearward direction along the centerline axis 37 of aerosol dispensingapparatus 20. The steeply sloped approximately vertical portion 42 ofsignal 38 causes an abrupt forward movement of the flexible diaphragm 32along the centerline axis 37 of apparatus 20. The sawtooth waveformsignal 38 of FIG. 3 may have a frequency of up to 1000 hertz.

The inner portion of housing 28 forms a chamber 44 which has containedtherein a medication which may be either in liquid form or powderedform. The jitter component 40 of the sawtooth waveform signal 38fluidizes the medication within chamber 44 above the upper surface ofdiaphragm 32. Fluidizing the medication suspends the medication in airwithin chamber 44 to form an aerosol medication which is designatedgenerally by the reference numeral 46.

Each cycle of the sawtooth waveform signal of FIG. 3 generates one ringvortex of the train of ring vortices 22 with the ring vortex beinggenerated during vertical portion 42 of signal 38. During the rampportion of the signal 38 air from the atmosphere is drawn into chamber44 of aerosol dispensing apparatus 20.

Referring now to FIGS. 2 and 3, there is shown another embodiment of theaerosol dispensing apparatus which is designated generally by thereference numeral 50. Aerosol dispensing apparatus 50 also dispenses amedicated vapor or aerosol medication into the lungs of a patient havingasthma or a like medical condition. Aerosol dispensing apparatus 50generates a train of ring vortices 52 which exits dispensing apparatus50 flowing through a sharp edged orifice or opening 54 located at thetop wall 55 of apparatus 50 in the manner indicated by arrow 56 prior toentering the lungs of a patient. The medicated vapor then enters thebronchial tubes and the alveolar air sachs of the patient's lungstreating the patient's medical condition.

Aerosol dispensing apparatus 50 has a generally rectangular shapehousing 58 which includes top wall 55. Housing 58 is partitioned into anupper chamber 60 and a lower chamber 62 by a speaker assembly supportwall 64. Speaker assembly support wall 64, which is locatedapproximately at the center point of housing 58, provides the supportstructure for a speaker assembly 66 which is identical to speakerassembly 30 of dispensing apparatus 20 of FIG. 1.

There is attached to the bottom of wall 70 of housing 58 a generallyrectangular shaped aerosol generator 72 which provides medicatedparticles under pressure into lower chamber 62 through opening 76 withinwall 70 as is best indicated by arrow 71. Lower chamber 62 of aerosoldispensing apparatus operates as a mixing chamber mixing medicatedparticles with air in lower chamber 62 resulting in a medicated vapor(indicated generally by the reference numeral 74).

After the mediated vapor 74 is formed in lower chamber 62. Medicatedvapor 74 then flows through openings 78 and 80 within speaker assemblysupport wall 64 as indicated by arrows 82 and 84. The upper chamber 60and speaker assembly 66 of aerosol dispensing apparatus 50 function inexactly the same manner as chamber 44 and speaker assembly 30 of theaerosol dispensing apparatus 50 of FIG. 1. Speaker assembly 66 isconnected to a sawtooth waveform generator which generates and thenprovides the sawtooth waveform signal 38 (FIG. 3) including jittercomponent 40 to the winding of speaker assembly 66 to drive the coneshaped flexible diaphragm of speaker assembly 66 with a reciprocatingmotion. This reciprocating motion of the flexible diaphragm of speakerassembly 66 generates the train of ring vortices 52 which carriesmedicated vapor 74 to the patient's lungs.

Referring now to FIGS. 3, 4 and 5, there is shown in FIG. 4 a thirdembodiment of an aerosol dispensing apparatus, designated generally bythe reference numeral 86, for providing a medicated vapor or aerosolmedication to the lungs of a patient having asthma or a like medicalcondition. Aerosol dispensing apparatus 86 comprises housing 88 whichincludes an orifice plate 90 extending across the top portion of housing88 and a speaker assembly 92 mounted on a bottom portion of housing 88.Speaker assembly 92 when energized drives a cone shaped flexiblediaphragm 94 of the speaker assembly 92 with a reciprocating motion.Speaker assembly 92 also has a coil (not illustrated) which is coupledto flexible diaphragm 94 and a permanent magnet 96.

Connected to the winding of speaker assembly 92 is a sawtooth waveformgenerator which is identical to the sawtooth waveform generator 36illustrated in FIG. 1. The sawtooth waveform generator provides thesawtooth waveform signal 38 to the winding of speaker assembly 92driving flexible diaphragm 94 which results in the reciprocating motionof flexible diaphragm 94.

The inner portion of housing 88 between the inner surface of flexiblediaphragm 94 and an orifice support structure 100 of housing 88 forms amedication holding chamber 102. Medication holding chamber 102 hascontained therein a medication which may be either in liquid form orpowdered form. The orifice support structure 100 also has a diaphragmsupport rim 104 which attaches the cone shaped flexible diaphragm 94 toorifice support structure 100.

Housing 88 of aerosol dispensing apparatus 86 has therein a gaseousholding chamber 106 which is located generally between the outer surfaceof flexible diaphragm 94 and the inner surface of housing 88.

Orifice support structure 100 of aerosol dispensing apparatus 86includes a plurality of counter flow orifices 108, 110 and 112 and isthe support structure for the counter flow orifices 108, 110 and 112 ofaerosol dispensing apparatus 86. FIG. 5 illustrates in detail each ofthe counter flow orifices 108, 110 and 112 of aerosol dispensingapparatus 86. It should be understood that the number of counter floworifices of aerosol dispensing apparatus 86 may vary in accordance withthe following: (1) the medication being dispensed by apparatus 86; (2)the desired ring vortex number, size and position geometry; and (3) theillness suffered by the patient being treated.

As is best illustrated in FIG. 5 each of the counter flow orifices 108,110 and 112 of apparatus 86 comprises a cylindrical shapedorifice/opening 116 with an enlarged lower end portion 117 whichoperates as a plenum and an open concentric ring 118 positioned aboutthe periphery of the upper end of orifice 116.

The upper end portion of orifice 116 communicates with the atmosphere120, while the enlarged lower end portion 117 of orifice 116 is coupledto medication holding chamber 102 of housing 88. In a like manner, oneend of concentric ring 118 communicates with the atmosphere 120, whilethe opposite end of ring 118 is coupled to air passageways 122 withinorifice support structure 100. Air passageways 122 couple the concentricring 118 of each of the counter flow orifices 108, 110 and 112 ofapparatus 86 to gaseous holding chamber 106. This allows for air flowfrom the atmosphere 120 through the concentric rings 118 of counter floworifices 108, 110 and 112 to gaseous holding chamber 106.

The top end 124 of the concentric ring 118 of each counter flow orifice108, 110 and 112 is tapered or beveled to provide a sharp edge at theouter wall 126 of concentric ring 118 and the inner wall 128 ofconcentric ring 118 (as depicted in FIG. 5). The length of the taperedtop end 124 of concentric ring 118 is about two and one half times thewall thickness of concentric ring 118.

Each cycle of the sawtooth waveform signal of FIG. 3 generates one ringvortex of the train of ring vortices 130, 132 and 134 respectively fromcounter flow orifices 108, 110 and 112. The ring vortex of each train ofring vortices 130, 132 and 134 is generated during the vertical portion42 of signal 38. During the ramp portion of the signal 38 air from theatmosphere is drawn into medicated holding chamber 102 of aerosoldispensing apparatus 86.

Referring again to FIG. 5, it should be noted that each ring vortex isformed during vertical portion 42 of signal 38 (FIG. 3) by medicatedvapor being expelled from chamber 102 through cylindrical shaped orifice116 (as indicated by arrow 136) and the simultaneous drawing of air fromthe atmosphere 120 through concentric ring 118 (as indicated by arrow138) into gaseous holding chamber 106.

Referring to FIG. 6, there is shown an aerosol dispensing apparatus,designated generally by the reference numeral 140, for dispensing amedicated vapor into the lungs of a patient having asthma or a likemedical condition. Aerosol dispensing apparatus 140 generates a ringvortex 142 which exits dispensing apparatus 140 through a contouredHexcel or honeycomb flow structure 144 located at an upper portion ofaerosol dispensing apparatus 140. The medicated vapor of ring vortex 142then enters the bronchial tubes and the alveolar air sachs of thepatient's lungs treating the patient's medical condition.

Contoured Hexcel structure 144 which comprises a plurality of elongatedhexagonal shaped fluid passageways 146 of varying lengths shapes the airvelocity profile 148 (by selective flow drag) to match the velocityprofile 150 of the emerging ring vortex 142. The direction ofpropagation of the emerging ring vortex 142 is generally indicated byarrow 151.

As shown in FIG. 6, contoured Hexcel structure 144 is formed by ahemispherical shaped structure 152 and a quarter circle shaped structure154 which is positioned about the perimeter of hemispherical shapedstructure 152.

Aerosol dispensing apparatus 140 comprises housing 158 which hascontoured Hexcel structure 144 affixed to a top portion thereof and aspeaker assembly 160 affixed to housing 158 at a bottom portion thereof.Speaker assembly 160 when energized drives a cone shaped flexiblediaphragm 162 of the speaker assembly 160 with a reciprocating motion.Connected to speaker assembly 160 is a sawtooth waveform generator 164.Generator 164, in turn, generates and then provides the sawtoothwaveform signal 38 of FIG. 3 which includes a jitter component 40 to thespeaker assembly 160 driving cone shaped flexible diaphragm 162 whichresults in the reciprocating motion of flexible diaphragm 162.

Housing 158 of aerosol dispensing apparatus 140 also has an air intakepassageway 156 which is coupled to quarter circle shaped structure 154allowing air from the atmosphere to be drawn into housing 158 viapassageway 156 (as indicated by arrow 166). There is also located withinhousing 158 a plurality of vent holes 168 which allow for air flow fromthe atmosphere through passageway 156 to gaseous holding chamber 170which surrounds the outer surface of flexible diaphragm 162.

At this time it should be noted that aerosol dispensing apparatus 140may include a septum ring which is positioned between structure 152 andstructure 154 of apparatus 140. The septum ring would be a thincylindrical shaped structure having a height approximating the height ofstructure 152 and structure 154. The septum ring would separate theemerging ring vortex 142 flow (indicated by arrow 151) from counterflowair drawn into housing 158 via passageway 156 (indicated by arrow 166).

By utilizing elongated hexagonal shaped fluid passageways 146 of varyinglengths, such as found in contoured Hexcel structure 144, a velocityprofile of the type illustrated in FIG. 6 can be tailored for ringvortex 142. The following analysis illustrates the relationship of dragduct length of the passageways 146 of structure 144 to the desiredvelocity profile for ring vortex 142.

The first step is to calculate velocity head, H_(i), of the air flowfrom any arbitrary passageway 146 of structure 144, which will beidentified as the i-th passageway. The following passageway defines therelationship between velocity V_(i) and velocity head H_(i).

    V.sub.i =√2gH.sub.i                                 (1)

Velocity head loss H_(DD) in the i-th passageway 146 is determined bythe following equation.

    H.sub.DD =H.sub.o -H.sub.i                                 (2)

where H_(o) is the maximum velocity head generated by the motion of coneshaped flexible diaphragm 162 of speaker assembly 160.

The velocity head loss H_(DD), resulting from flow through a passageway146 of contoured Hexcel structure 144 is given by the Darcy-Weisbechequation: ##EQU1## where: f=friction factor due to viscous and turbulentenergy losses.

(l/R)=the length, l, to hydraulic radius, R, ratio of the passageway146.

V=the velocity of air through the passageway 146 which is constant dueto the assumed incompressibility of air and the constant cross sectionof the passageway.

g=acceleration of gravity.

To determine the friction factor, f, the Reynolds number N_(Re) (whichis set forth in the following equation) must be determined. ##EQU2##where: ρ=the density of air.

μ=the viscosity of air.

The friction factor, f, is a function of N_(Re) according to thefollowing equations. For N_(Re) <2000 the following equation is used todetermine f.

    f=4N.sub.Re                                                (5)

For N_(Re) =3000 to 10,000 the following equation is used to determinef. ##EQU3## where: e=surface roughness of the inner surface ofpassageway.

log=log to base 10.

For N_(Re) >10,000 the following equation is used to determine f.##EQU4## For smooth passageways, surface roughness may be neglected andthe following equation may be used to determine f for N_(Re). ##EQU5##

The length l of the i-th passageway 146 is determined using equation (3)and the definition of the hydraulic radius, R, of a non-circular flowchannel which is determined according to the following equation.##EQU6## where the flow passage cross-section of a passageway 146 of thecontoured Hexcel structure 144, A_(x-sect), is given by:

    A.sub.x-sect =1.5√3×S.sup.2                   (10)

and the wetted perimeter, P_(wp) is given by: ##EQU7## where S is thelength of a side of the passageway 146.

The initial velocity head provided by the speaker assembly 160 andflexible diaphragm 162 H_(o) is diminished by the velocity head loss,H_(DD), due to flow friction as air flows through the i-th passageway146. From equations (1) and (2) the air velocity from the outlet end ofthe i-th passageway 146 is given by the following equation.

    V.sub.i =√2g(H.sub.o -H.sub.DD)                     (12)

The velocity profile of the ring vortex 142 may then be determined bythe following equation which is the law of Biot-Savart. The law ofBiot-Savart states that in a free vortex, the velocity about the vortexcore filament varies inversely with the distance r_(i). ##EQU8## where kis a constant having a magnitude which depends on the strength of thevortex.

To determine the passageway length at the center of the orifice, wherer_(i) =r_(c), the radius of the inner orifice, the velocity V_(i) ofequation (1) is set equal to a value appropriate to the free airpropagation velocity of the departing ring vortex 142. From equation (1)H_(c) is determined and used in equation (2) to determine H_(DD) for thevelocity head loss in the center passageway 146. The appropriatefriction factor may be determined from equation 5, 6 or 7; the centerpassageway 146 length, l, may be calculated from equation (3). Equation(13) may now be used to calculate the value of the strength of the ringvortex K.

With the value of k available, the velocity at any radial distance fromthe edge of the inner orifice can be calculated, and with equations (1)and (2), velocity head loss H_(DD) can be determined. In the same manneras for the center passageway, the length l for each passageway 146 ofcontoured Hexcel structure 144 can be calculated.

It should be noted from equation (2) that increasing velocities lead todecreasing velocity head loss H_(DD) and thus decreasing passagewaylength, as shown in FIG. 6. It is therefore advisable to start near theperiphery of structure 152 with a value of r_(i) =1/10 r_(c) and selecta minimal length for the outer passageways 146.

From the foregoing, it may readily be seen that the present inventioncomprises a new, unique and exceedingly useful aerosol dispensingapparatus for effectively providing medication in a mist or vapor formto the lungs of a patient which constitutes a considerable improvementover the known prior art. Obviously many modifications and variations ofthe present invention are possible in light of the above teachings. Itis therefore to be understood that within the scope of the appendedclaims, the invention may be practiced otherwise than as specificallydescribed.

What is claimed is:
 1. An aerosol dispensing apparatus comprising:ahousing having a forward wall and an inner portion, the inner portion ofsaid housing forming a chamber having a medication contained therein; aspeaker assembly mounted on a bottom portion of said housing, saidspeaker assembly having a cone shaped flexible diaphragm; a signalgenerator connected to said speaker assembly, said signal generatorproviding a sawtooth waveform signal of a predetermined frequency tosaid speaker assembly, said sawtooth waveform signal having a rampportion which includes a jitter component, the jitter component of saidsawtooth waveform signal fluidizing said medication within said chamberto form an aerosol medication; said sawtooth waveform signal driving thecone shaped flexible diaphragm of said speaker assembly resulting in areciprocating motion at said predetermined frequency for said coneshaped flexible diaphragm; said housing having an edged shaped orificecentrally located within the forward wall of said housing, said edgedshaped orifice communicating with said chamber allowing said aerosolmedication to exit said chamber and flow through said edged shapedorifice to form a ring vortex of aerosol medication; the reciprocatingmotion of said cone shaped flexible diaphragm at said predeterminedfrequency causing said aerosol dispensing apparatus to generate a trainof said ring vortices of aerosol medication.
 2. The aerosol dispensingapparatus of claim 1 wherein the predetermined frequency of saidsawtooth waveform signal is between one hertz and one thousand hertz. 3.An aerosol dispensing apparatus comprising:a rectangular shaped housinghaving a front wall and a rear wall, said rear wall having a centrallylocated opening; an aerosol generator affixed to the rear wall of saidrectangular shaped housing; a support wall centrally located within saidrectangular shaped housing, said support wall partitioning saidrectangular shaped housing to form a lower chamber and an upper chamber,said support wall having a plurality of openings; said aerosol generatorproviding particles of a medication under pressure through the centrallylocated opening of said rear wall into said lower chamber, said lowerchamber mixing the particles of said medication with air to form anaerosol medication, said aerosol medication flowing through theplurality of openings within said support wall into said upper chamber;a speaker assembly mounted on said support wall, said speaker assemblyhaving a cone shaped flexible diaphragm; a signal generator connected tosaid speaker assembly, said signal generator providing a sawtoothwaveform signal of a predetermined frequency to said speaker assembly,said sawtooth waveform signal driving the cone shaped flexible diaphragmof said speaker assembly resulting in a reciprocating motion at saidpredetermined frequency for said cone shaped flexible diaphragm; saidrectangular shaped housing having an edged shaped orifice centrallylocated within the front wall of said housing, said edged shaped orificecommunicating with said upper chamber allowing said aerosol medicationto exit said upper chamber and flow through said edged shaped orifice toform a ring vortex of aerosol medication; the reciprocating motion ofsaid cone shaped flexible diaphragm at said predetermined frequencycausing said aerosol dispensing apparatus to generate a train of saidring vortices of aerosol medication.
 4. The aerosol dispensing apparatusof claim 3 wherein the predetermined frequency of said sawtooth waveformsignal is between one hertz and one thousand hertz.
 5. The aerosoldispensing apparatus of claim 3 wherein said sawtooth waveform signalhas a ramp portion which includes a jitter component.